In the use of material handling vehicles, such as lift trucks, first and second chain assemblies are moved by a power means and function to elevate and lower the carriage. Under various conditions, such as uneven loading of the carriage, uneven ground or substrate upon which the vehicle is resting, and others, the force subjected on one of the chain assemblies is often considerably greater than the force on the other chain assembly. This unevenness of forces places considerable stresses on associated elements of the vehicle which sometimes damages the vehicle and/or causes an increased wear rate which represents waste.
This invention therefore resides in means for controlling relative forces on the chains.